^That's not how it works. When you introduce a character as a supporting character, people want to see that character again: as a supporting character. When you introduce them as a main character, they want to know more about their story, and so Captain America is getting a sequel, and Black Widow is not getting a solo movie. She's a more beloved character, but she's a beloved supporting character. That's what you're getting if you make BP a supporting character -> No BP solo movie.